Analysis of the utility of a rapid vesicle isolation method for clinical strains of Pseudomonas aeruginosa

Pseudomonas aeruginosa, a pathogen capable of causing diseases ranging from mild to life-threatening, has a large arsenal of virulence factors. Notably, extracellular vesicles have emerged as significant players in the pathogenesis of this organism. However, the full range of their functions is still being studied and difficulties related to vesicle purification (long protocols, low yields and specialized instruments) have become a major obstacle for their characterization. In this context, the utility of rapid new methods of vesicle isolation from clinical strains is still unknown. Here we analyze the utility of the ExoBacteria OMV isolation kit for a collection of clinical strains of P. aeruginosa. We first phenotypically characterized 15 P. aeruginosa strains to ensure that our samples were heterogenous. We then determined the best conditions for purifying vesicles from P. aeruginosa PAO1 reference strain by the rapid method and used them to isolate vesicles from clinical strains. Our results indicated that M9 minimal medium is the best for obtaining high purity with the rapid isolation kit. Although we were able to isolate vesicles from at least four strains, the low yield and the large number of strains with unpurifiable vesicles showed that the kit was not practical or suitable for clinical strains. Our findings suggest that although fast procedures for vesicle purification can be of great utility for E. coli, the more complex phenotypes of clinical isolates of P. aeruginosa are a challenge for these protocols and new alternatives/optimizations need to be developed.